1. Field of the Invention
The present invention relates to spectacles that include a magnifier to thereby enable a wearer to see a magnified view of a portion of an object being viewed when desired.
2. Prior Art
Certain delicate medical procedures such as ophthalmologies vascular inosculations and nerve operations often require the surgeon to use microscope so as to see a magnified view of the fine tissues being operated on. Although a fixed-type microscope is sometimes used it has a limited field of view and since a microscope also has a shallow depth of field, focussing on various parts of a non-planar object requires sequential focusing operations. Moreover, where the affected part to be operated on can be temporarily seen by the naked eyes, the field of view is impaired by the fixed microscope, thereby making its use unsatisfactory.
Japanese Utility Model Laid-Open Publication No. 52122/1980 discloses spectacles which include magnifying elements fixedly mounted in respective mounting holes bored approximately in the center of each of the two lenses thereof. During an operation, a surgeon wears the spectacles like normal spectacles, and when he needs to see an enlarged view of an affected part, he peeps into the magnifier, whereas when this is not necessary he can shift his eyes and look at the affected part through the main lenses. For persons who require correction of visual abnormalities such as myopia, hypermetropy and astigmatisms, if the refractive index of the lenses are selected to suit the wearer, the visual power equal to routine-use spectacles may be obtained.
However, in the aforesaid spectacles, the focal point of the magnifying elements attached to the lenses are, i.e., a preset change in focal point during use is substantially impossible. Accordingly, during an operation it is necessary to always maintain a certain distance from the eyes to the affected part. This is very burdensome to a surgeon wearing the spectacles and may interfere with his ability to concentrate on the operation being conducted. Furthermore, frequent deviation in focal point resulting from movement of the wearer and movement of the magnified object (an object to be seen) may cause asthenopia, deterioration of vision, etc., if the spectacles are worn for a long period of time.